Image improvement for alignment through incoherent illumination blending

Abstract

Methods and apparatuses are provided that determine an offset between actual feature/mark locations and the designed feature/mark locations in a maskless lithography system. For example, in one embodiment, a method is provided that includes opening a camera shutter in a maskless lithography system. Light is directed from a configuration of non-adjacent mirrors in a mirror array towards a first substrate layer. An image of the first substrate layer on a camera is captured and accumulated. Light is directed and images are captured repeatedly using different configurations of non-adjacent mirrors to cover an entire field-of-view (FOV) of the camera on the first substrate layer. Thereafter, the camera shutter is closed and the accumulated image is stored in memory.

We claim: 
     
       1. A method comprising:
 opening a camera shutter in a maskless lithography system; 
 directing light from a first semi-isolated mirror configuration in a mirror array towards a first substrate layer; 
 capturing and accumulating a first image of the first substrate layer on a camera; 
 directing light from a second semi-isolated mirror configuration in the mirror array towards a first substrate layer; 
 capturing and accumulating a second image of the first substrate layer on the camera; 
 closing the camera shutter; 
 storing the accumulated first and second images in memory; 
 forming a third image from the first and second images; and 
 detecting an actual alignment mark in the third image. 
 
     
     
       2. The method of  claim 1  further comprising:
 measuring an actual alignment mark location on the first substrate layer from the third image by using image processing; 
 comparing designed alignment mark locations for the first substrate layer to the actual alignment mark location; and 
 determining, from the comparing designed alignment mark location for the first substrate layer, an offset of the actual alignment mark locations on the first substrate layer. 
 
     
     
       3. The method of  claim 1  wherein the light is at a wavelength that is different than a wavelength of light used to etch. 
     
     
       4. The method of  claim 1  further comprising:
 opening the camera shutter; 
 directing light from the first semi-isolated mirror configuration in the mirror array towards a second substrate layer that is on top of the first substrate layer; 
 capturing and accumulating a fourth image of the second substrate layer on the camera; 
 directing light from the second semi-isolated mirror configuration in the mirror array towards the second substrate layer; 
 capturing and accumulating a fifth image of the second substrate layer on the camera; 
 closing the camera shutter; 
 forming a sixth image from the fourth and fifth images; and 
 detecting the actual alignment mark in the sixth image. 
 
     
     
       5. The method of  claim 4  further comprising:
 measuring the actual alignment mark location on the second substrate layer from the sixth image using image processing to determine the actual mark location; 
 comparing a designed alignment mark location for the second substrate layer to the actual alignment mark location; and 
 determining, from the comparing designed alignment mark location for the second substrate layer, an offset of the actual alignment mark location on the second substrate layer. 
 
     
     
       6. The method of  claim 4  further comprising:
 measuring actual alignment mark location on the second substrate layer from the sixth image of the second substrate layer; 
 comparing designed alignment mark location for the first substrate layer to the actual alignment mark locations on the second substrate layer; and 
 determining, from the comparing designed alignment mark locations for the second substrate layer, an offset to align the actual alignment mark locations on the second substrate layer to the designed alignment mark locations on the first substrate layer. 
 
     
     
       7. A method comprising:
 opening a camera shutter in a maskless lithography system; 
 moving a substrate; 
 directing light from a first semi-isolated configuration of a mirror array to the moving substrate; 
 capturing and accumulating, a first set of images in the camera to cover an entire camera field-of-view (FOV) on a first substrate layer on the moving substrate; 
 directing light from a second semi-isolated configuration of the mirror array to the moving substrate; 
 capturing and accumulating a second set of images in the camera to cover an entire camera field of view (FOV) on a first substrate layer on the moving substrate; 
 closing the camera shutter; 
 storing the accumulated first and second sets of images in memory; 
 forming a third image from the first and second sets of images; and 
 detecting an actual alignment mark in the third image. 
 
     
     
       8. The method of  claim 7  further comprising:
 measuring an actual alignment mark location on the first substrate layer from the third image by using image processing; 
 comparing a designed alignment mark location for the first substrate layer to the actual alignment mark location; and 
 determining, from the comparing designed alignment mark location for the first substrate layer, an offset of the actual alignment mark location on the first substrate layer. 
 
     
     
       9. The method of  claim 7  wherein the light is at a wavelength that is different than a wavelength of light used to etch. 
     
     
       10. The method of  claim 7  further comprising:
 moving the substrate; 
 opening the camera shutter; 
 directing light from the first semi-isolated configuration of the mirror array to the moving substrate; 
 capturing and accumulating, continuously, a fourth set of images to cover the entire FOV on a second substrate layer on the moving substrate; 
 directing light from the second semi-isolated configuration of a mirror array to the moving substrate; 
 capturing and accumulating, continuously, a fifth set of images to cover the entire FOV on a second substrate layer on the moving substrate; 
 closing the camera shutter; 
 storing the accumulated fourth and fifth sets of images in memory 
 forming a sixth image from the fourth and fifth sets of images; and 
 detecting an actual alignment mark in the sixth image. 
 
     
     
       11. The method of  claim 10  further comprising:
 measuring the actual alignment mark location on the second substrate layer from the sixth image by using image processing; 
 comparing a designed alignment mark location for the second substrate layer to the actual alignment mark location on the second substrate layer; and 
 determining, from the comparing designed alignment mark location for the second substrate layer, an offset of the actual alignment mark location on the second substrate layer. 
 
     
     
       12. The method of  claim 10  further comprising:
 measuring the actual alignment mark location on the second substrate layer from the sixth image by using image processing; 
 comparing the designed alignment mark location for the first substrate layer to the actual alignment mark location on the second substrate layer; and 
 determining, from the comparing designed alignment mark location for the second substrate layer, an offset to align the actual alignment mark location on the second substrate layer to the designed alignment mark location on the first substrate layer. 
 
     
     
       13. A lithography system comprising:
 a light source; 
 a mirror array is adapted to have a first semi-isolated mirror configuration and a second semi-isolated mirror configuration, to receive light from the light source and is adapted to reflect light towards a substrate layer; 
 a beam splitter adapted to receive the light reflected from the mirror array and light reflected from the substrate layer; 
 a camera coupled to the beam splitter and adapted to capture and accumulate images on the substrate layer that are visible due to the light reflected from the substrate layer; and 
 a processor coupled to the light source, the mirror array to select at least one of the first and second semi-isolated mirror configurations, the beam splitter, and the camera, the processor configured to:
 capture a first image, using the camera, of the substrate layer that is visible due to the reflected light to the substrate layer from the mirror array in the first semi-isolated mirror configuration; 
 capture a second image, using the camera, of the substrate layer that is visible due to the reflected light to the substrate layer from the mirror array in the second semi-isolated mirror configuration; 
 form a third image from the first and second image; and 
 detect an alignment mark in the third image. 
 
 
     
     
       14. The system of  claim 13  further comprising:
 a stage that is adapted to support the substrate layer, wherein a position of the stage is fixed with respect to the substrate layer, the stage is adapted to receive instructions from the process to move in at least one of a direction parallel to an X-axis and a direction parallel to a Y-axis, while the camera captures images. 
 
     
     
       15. The system of  claim 13  wherein the captured images are one of an alignment mark and a feature on the substrate layer. 
     
     
       16. The system of  claim 13  wherein the processor is adapted to change the configuration of the mirror array to at least one other configuration of the first and second semi-isolated mirror configuration while the camera captures images. 
     
     
       17. The system of  claim 13  wherein,
 the mirror array is adapted to receive light from the light source and reflect light towards a different substrate layer; 
 the beam splitter is adapted to receive light reflected from the different substrate layer; and 
 the camera is adapted to capture and accumulate images on the different substrate layer that are visible due to the light reflected from the different substrate layer.